Scientists boost efficacy of protein-based COVID-19 vaccine, boost immune response 25-fold
Details of the study are described in a new paper published today (August 31, 2022) in the journal ACS Infectious Diseases.
While the first COVID-19 vaccines licensed in the U.S. used state-of-the-art mRNA genetic technology, the tried-and-true strategy of using the pathogen’s proteins could lead to vaccines that are cheaper to manufacture and easier to store. So far, the U.S. Food and Drug Administration (FDA) has approved only one protein vaccine against SARS-CoV-2, made by Novavax. However, many currently available vaccinations against other diseases rely on proteins or fragments of proteins, and these shots contain adjuvants to increase their effectiveness.
Scientists have discovered that a molecule derived from alpha-galactosylglyceride (αGC), a compound derived from marine sponges, can act as an adjuvant. They work by stimulating a small population of immune cells that are important in defending the body against viral infections. Rui Luo, Zheng Liu and their colleagues have engineered a version of αGC to significantly enhance the immune response elicited by protein-based COVID-19 vaccines.
The group made four analogs of αGC. They added each to an experimental vaccine containing the SARS-CoV-2 spike protein, which the virus uses to infect cells. The mice were injected three times over 29 days, and the researchers tracked their immune responses until day 35.
To measure the effects of adjuvants, scientists took a closer look at various aspects of immune function, including two ways the immune system eliminates pathogens: through T cells (which kill diseased cells directly) and antibodies (immune proteins that grab onto invading microbes). .
None of the four substances boosted T-cell responses, but they all allowed the immune system to produce antibodies that were far more capable of interfering with the virus. A similar substance, known as αGC-CPOEt, elicited antibodies with the greatest neutralizing capacity — 25 times greater than what an unadjuvanted vaccine could elicit.
According to the researchers, these results suggest that αGC-CPOEt deserves further study as a potential adjuvant against COVID-19 and other infectious diseases.